1 files changed, 96 insertions, 0 deletions
diff --git a/server/noise.lua b/server/noise.lua
new file mode 100644
index 0000000..1480448
--- /dev/null
+++ b/server/noise.lua
@@ -0,0 +1,96 @@
+local Pos = require"common.coords".Pos
+local tau = 2*math.pi
+
+math.randomseed(os.time())
+
+local function random_unit_vec()
+	local theta = math.random()*tau
+	return Pos.make(math.cos(theta),math.sin(theta))
+end
+local function lerp(a,b,t) return (1-t)*a + t*b end
+local function smoothstep(x)
+	if x<0 then return 0 end
+	if x>1 then return 1 end
+	return x*x*(3 - 2*x)
+end
+local function slerp(a,b,t) return lerp(a,b,smoothstep(t)) end
+
+local NoiseGen = {}
+NoiseGen.__index = NoiseGen
+function NoiseGen.make()
+	local grid = {}
+	setmetatable(grid,{__index=function(t,k) t[k] = {} return t[k] end})
+	return setmetatable({grid=grid},NoiseGen)
+end
+function NoiseGen.vertex(self,ix,iy)
+	local v = self.grid[ix][iy]
+	if v then return v end
+	vv = random_unit_vec()
+	self.grid[ix][iy] = vv
+	return vv
+end
+
+function NoiseGen.at(self,x,y)
+	local x0 = math.floor(x)
+	local y0 = math.floor(y)
+	local x1 = x0 + 1
+	local y1 = y0 + 1
+
+	local v00 = self:vertex(x0,y0)
+	local v01 = self:vertex(x0,y1)
+	local v10 = self:vertex(x1,y0)
+	local v11 = self:vertex(x1,y1)
+
+	local p = Pos.make
+	local d00 = v00:dot(p(x-x0,y-y0))
+	local d01 = v01:dot(p(x-x0,y-y1))
+	local d10 = v10:dot(p(x-x1,y-y0))
+	local d11 = v11:dot(p(x-x1,y-y1))
+
+	local q0 = slerp(d00,d01,y-y0)
+	local q1 = slerp(d10,d11,y-y0)
+	local z  = slerp(q0,q1,x-x0)
+	return z
+end
+
+local NoiseAgg = {}
+NoiseAgg.__index = NoiseAgg
+function NoiseAgg.make(things)
+	return setmetatable({things=things or {}},NoiseAgg)
+end
+function NoiseAgg.make_perlin_octaves(nocts)
+	local things = {}
+	for i=1,nocts do
+		table.insert(things,{amp=2^i,scale=2^(nocts-i),gen=NoiseGen.make()})
+	end
+	return NoiseAgg.make(things)
+end
+function NoiseAgg.at(self,x,y)
+	local n = 0
+	local t = 0
+	assert(#self.things>0,"can't generate noise with no noise things")
+	for _,thing in ipairs(self.things) do
+		local gen,scale,amp = thing.gen,thing.scale,thing.amp
+		n = n + amp
+		t = t + gen:at(x*scale,y*scale)*amp
+	end
+	return t/n
+end
+
+-- local chars = "$@B%8&WM#*oahkbdpqwmZO0QLCJUYXzcvunxrjft/\\|()1{}[]?-_+~<>i!lI;:,\"^`'. "
+
+-- local scale = 3
+
+-- for x=1,10-10/40,10/40 do
+-- 	for y = 1,10-10/60,10/60 do
+
+-- 		local n = at(1+(x-1)/scale,1+(y-1)/scale)
+-- 		local nn = (n +1)/2
+-- 		local nnn = 1+nn*#chars
+-- 		local c = chars:sub(nnn,nnn)
+-- 		io.write(c)
+-- 	end
+-- 	io.write("\n")
+-- end
+
+return {NoiseGen=NoiseGen,NoiseAgg=NoiseAgg}